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Crashed capsule may still reveal solar secrets

Much of the science from NASA’s Genesis space capsule, which crashed in Utah on 8 September, will probably be salvaged, mission scientists say.

Initial inspections of the ruptured capsule at an airbase near the crash site suggest many, if not all, of the capsule’s hexagonal particle collectors are broken. But contamination from dirt and moisture may not be as widespread or damaging as originally thought, Genesis team members said Friday.

The capsule spent 27 months in space, collecting charged particles blown on the solar wind from the Sun’s outermost layer. That layer is thought to be nearly unchanged from the cloud of gas and dust from which the solar system formed about 4.5 billion years ago.

Genesis was designed to improve estimates of the cloud’s composition by at least threefold in order to test theories of how the solar system evolved. Its most important target was oxygen, which exists on different planets in different ratios of its three most common isotopes.

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“If we understand what we start with and what we end up with, we can try to understand what kind of thermal environments the planets went through,” Benton Clark, a Genesis team member at Lockheed Martin Space Systems, told New Scientist.

Oxygen trap

The solar wind is 99% ions of hydrogen and helium. So mission planners designed an instrument to trap oxygen at concentrations at least 20 times greater than normally found in the solar wind.

On Friday, mission scientists said they could see two of the four wedges housing these oxygen ions when they peeked inside the cracked science canister with a flashlight and a mirror on a stick.

“We’re really quite confident we can achieve a high degree of success from a science point of view,” said team member Roger Wiens of Los Alamos National Laboratory in New Mexico.

Genesis scientists described a mixed outlook on the mission’s other top targets, nitrogen and carbon. Gold foil used to collect isotopes of nitrogen, which could lend insight into the evolution of planetary atmospheres, was found intact.

But Don Burnett, the mission’s principal investigator at the California Institute of Technology in Pasadena, California, said an experiment using some of the mission’s silicon wafers to study carbon isotopes was “very challenged”. This is because of carbon contamination – “the dirt is full of it and the atmosphere is full of it,” he said.

Sapphire and diamond

Genesis used five arrays of coaster-sized hexagonal wafers to collect solar wind ions. These were made of ultra-pure materials – including silicon, germanium, sapphire, and diamond – to make studying particular elements easier in labs back on Earth.

The ions probably embedded themselves a few hundred atomic lengths (50 nanometres) into these wafers. “That is very close to the surface,” says Wiens. Cleaning techniques would affect the surface by a few nanometres, he says, “so we have to be extremely careful”.

Clark said ultra-pure water, brushes, or air currents might be used to get rid of the dirt, which was “a little sticky and hard to get off” because the capsule had landed in Utah’s salt flats.

Burnett said the team might also consult with experts in the semiconductor industry. Gabor Somorjai, a chemist at the University of California, Berkeley, says a commonplace technique used to etch microelectronic circuits on computer chips could easily remove the debris with an accuracy of 1 nanometre. Called sputtering, it involves firing high-energy ions of an inert gas, such as argon or xenon, to remove a material’s surface.

Somorjai also said contamination from oxygen in the air was probably not a problem, as some of the wafer materials react with oxygen only at high temperatures, and the few minutes the capsule spent blazing into the atmosphere was probably not long enough to affect them.

NASA also announced Friday that Michael Ryschkewitsch, director of the Applied Engineering and Technology Directorate at the agency’s Goddard Space Flight Center in Maryland, would lead the investigation into the crash.